Gray's review provided a pivotal victory for Darwin: It gave his
highly controversial theory, which he had published the previous
December, the support of one of America's most respected scientists.
Gray proved a key and effective advocate for Darwin in the U.S.,
especially during 1860, when he thrice defeated in debate America's most
prominent scientist, the zoologist Louis Agassiz. Agassiz, a
creationist, resisted Darwin's theory ferociously. He did so both
because he disagreed and because he himself had become the country's
most famous scientist by beautifully articulating a vision of species as
works of God. He had built his career on this vision. He knew he had to
defeat Darwin or go down himself.